#define DEBUG 0
#include <bits/stdc++.h>
using namespace std;
#if DEBUG
// basic debugging macros
int __i__,__j__;
#define printLine(l) for(__i__=0;__i__<l;__i__++){cout<<"-";}cout<<endl
#define printLine2(l,c) for(__i__=0;__i__<l;__i__++){cout<<c;}cout<<endl
#define printVar(n) cout<<#n<<": "<<n<<endl
#define printArr(a,l) cout<<#a<<": ";for(__i__=0;__i__<l;__i__++){cout<<a[__i__]<<" ";}cout<<endl
#define print2dArr(a,r,c) cout<<#a<<":\n";for(__i__=0;__i__<r;__i__++){for(__j__=0;__j__<c;__j__++){cout<<a[__i__][__j__]<<" ";}cout<<endl;}
#define print2dArr2(a,r,c,l) cout<<#a<<":\n";for(__i__=0;__i__<r;__i__++){for(__j__=0;__j__<c;__j__++){cout<<setw(l)<<setfill(' ')<<a[__i__][__j__]<<" ";}cout<<endl;}
// advanced debugging class
// debug 1,2,'A',"test";
class _Debug {
public:
template<typename T>
_Debug& operator,(T val) {
cout << val << endl;
return *this;
}
};
#define debug _Debug(),
#else
#define printLine(l)
#define printLine2(l,c)
#define printVar(n)
#define printArr(a,l)
#define print2dArr(a,r,c)
#define print2dArr2(a,r,c,l)
#define debug
#endif
// define
#define MAX_VAL 999999999
#define MAX_VAL_2 999999999999999999LL
#define EPS 1e-6
#define mp make_pair
#define pb push_back
// typedef
typedef unsigned int UI;
typedef long long int LLI;
typedef unsigned long long int ULLI;
typedef unsigned short int US;
typedef pair<int,int> pii;
typedef pair<LLI,LLI> plli;
typedef vector<int> vi;
typedef vector<LLI> vlli;
typedef vector<pii> vpii;
typedef vector<plli> vplli;
// ---------- END OF TEMPLATE ----------
int C[300000];
vpii adjList[300000];
priority_queue<LLI> H[300000];
LLI m[300000],b[300000];
int p[300000];
int main() {
int i;
int N,M,P;
scanf("%d %d",&N,&M);
for (i = 1; i < N+M; i++) {
scanf("%d %d",&P,&C[i]);
adjList[P-1].pb(mp(i,C[i]));
}
int j;
for (i = N; i < N+M; i++) {
p[i] = i,m[i] = 1,b[i] = -C[i];
H[i].push(C[i]),H[i].push(C[i]);
}
for (i = N-1; i >= 0; i--) {
int h = -1;
for (j = 0; j < adjList[i].size(); j++) {
int v = adjList[i][j].first;
if ((h == -1) || (H[p[v]].size() > H[p[h]].size())) h = v;
}
p[i] = p[h];
for (j = 0; j < adjList[i].size(); j++) {
int v = adjList[i][j].first;
if (v != h) {
m[p[i]] += m[p[v]],b[p[i]] += b[p[v]];
while (!H[p[v]].empty()) H[p[i]].push(H[p[v]].top()),H[p[v]].pop();
}
}
while (m[p[i]] > 1) m[p[i]]--,b[p[i]] += H[p[i]].top(),H[p[i]].pop();
b[p[i]] -= C[i];
LLI x = H[p[i]].top();
H[p[i]].pop();
LLI y = H[p[i]].top();
H[p[i]].pop();
H[p[i]].push(x+C[i]),H[p[i]].push(y+C[i]);
}
printf("%lld\n",m[p[0]]*H[p[0]].top()+b[p[0]]);
return 0;
}
